This application is related to the following applications titled: Boat Propulsion Device Ser. No. 062,449; Exhaust System for a Boat Propulsion Device Ser. No. 062,227; Boat with Cavity for a Boat Propulsion Device Ser. No. 062,459; Boat Propulsion Device with Internal Exhaust Ser. No. 062,453 and Driveshaft Housing for a Boat Propulsion Device Ser. No. 062,228, all filed concurrent herewith on June 15, 1987.
The field of the present invention relates to a boat propulsion device and more particularly concerns a propeller drive for mounting from a hole in an aft bottom surface of a boat which is swingable under the boat for steering and for trimming/tilting of the drive.
Presently there are two general types of known pleasure boat drives; the first is the inboard outboard drive or stern drive and the second is the outboard.
The prior stern drive 10, shown in schematic form in Prior Art FIGS. 1a through 1d includes an engine 11 positioned horizontally in the boat 12 and an outdrive 13 depending from the boat 12. The outdrive 13 shown in illustrative block form by representative phantom lines has a horizontal upper portion extending rearwardly from the boat transom as shown by first block 14, a vertical middle portion extending downwardly or depending from the rearward end of the upper portion generally along the transom ending below the bottom of the boat as shown by the second block 15, and a horizontal lower portion extending rearwardly from the bottom of the vertical portion to a propeller 16 as shown by the third block 17.
The stern drive 10 includes drive-line shaft components which begin at the horizontal crankshaft of the engine 11 and extend to the propeller 16. As shown in FIG. 1a, these shaft components shown by representative heavy dashed lines include a horizontal upper drive shaft assembly 18 which includes a first portion 19, a second portion 20 and a connecting universal joint 21; a vertical drive shaft 22 and a propeller shaft 23.
The outdrive 13 is mounted on the transom 24 of the boat 12 with a gimbal assembly 25 as illustrated in FIG. 1d. The gimbal assembly 25 contains a vertical pivot 26 on vertical axis 27 and a horizontal pivot 28 on horizontal axis 29. The outdrive 13 turns from side-to-side as shown by arrow 27a on the vertical axis 27 for steering and swings up-and-down as shown by arrow 29a on the horizontal axis 29 for trimming/tilting.
Although the stern drive 10 has evolved into a satisfactory type boat drive, it has certain design complexities which increase the size and weight as well as the cost. One complexity is the outdrive 13 shown by the three blocks 14, 15, and 17 which is clearly not only heavy but also provides an overhanging weight which requires extra strength in certain components. Some of these components such as the horizontal pivot 28 of the gimbal assembly 25 must carry the entire weight of the outdrive 13. In addition, the large aluminum parts of the outdrive 13 are subject to cathodic and salt water corrosion.
The prior outboard 40 is shown in schematic form in Prior Art FIGS. 2a through 2c. The outboard 40 unlike the stern drive 10 is a unit assembly of a vertical engine 41, a midsection 42 positioned below the engine 41 and a lower unit 43 having a propeller 44. The outboard 40 is shown in block form by representative phantom lines in FIGS. 2a, 2b and 2c. The midsection 42 is shown by a fourth block 45 and the lower unit 43 by a fifth block 46.
The outboard 40 also contains drive-line components which begin at a vertical crankshaft of the engine 41 and extend to the propeller 44. These drive-line components are integral within the unit assembly and unlike the stern drive 10 have a fixed drive angle.
The outboard 40 is mounted on the transom 49 of boat 50 with a transom mounting bracket 51 and swivel bracket 52 as shown in FIGS. 2a and 2d. As shown in FIGS. 2c and 2d the swivel bracket 52 includes a vertical swivel bracket pivot 53 having a vertical swivel bracket pivot axis 54 and a horizontal swivel bracket pivot 55 having a horizontal swivel bracket pivot axis 56. The outboard 40 turns from side-to-side on the vertical swivel bracket pivot axis 54 as shown by the arrow 54a for steering and swings up-and-down on the horizontal swivel bracket pivot axis 56 as shown by the arrow 56a for trimming/tilting. Unlike the stern drive 10, the outboard vertical steering axis moves with the outboard movement as shown in FIG. 2d. This is best understood by comparing first steering axis 57 of the outboard in about full in-trim position with the second steering axis 58 of the outboard in about full up-tilt position.
Although the outboard 40 is a satisfactory boat drive, inherent in its design as a unit assembly for attachment over the transom is the need to support weight of the entire unit assembly off the transom of the boat. With small horsepower this is satisfactory, but as the horsepower becomes larger the weight and size places overhanging loads on the transom. The outboard 40 also requires a large engine cover or cowl which provides a bulky appearance. Also, clearance is required in the boat forward and inside the transom to accommodate the engine cowl when the engine is in the full up-tilt position. In addition, the steering arm 59, as shown in FIG. 2c, moves with the outboard 40 when the outboard pivots about the horizontal swivel bracket pivot axis 56. This motion is different at different trim/tilt positions resulting in the need for a complex boat steering system.
Other prior drives for boats mount through the bottom of the boat. These prior drive types are described in U.S. Pat. No. 2,209,302 to L. J. Johnson et al as well as in U.S. Pat. Nos. 2,976,836 and 3,164,122 to L. J. Fageol.